interface IShape {
    getPer():number,
    getArea():number,
}

let react:IShape = {
    getPer():number {
        return (10 + 5) * 2;
    },
    getArea():number {
        return 10 * 5;
    }
}

let circle:IShape = {
    getPer():number {
        return 2 * 5 * Math.PI;
    },
    getArea():number {
        return 5 * 5 * Math.PI;
    }
}